The present invention relates generally to interference relay channels and more particularly to improving rateless coding for multiuser interference relay channels.
In many wireless communication systems, when multiple source-destination pairs communicate, the transmission from the sources causes interference on the received signal in the other destinations when the communicating nodes are in the hearing vicinity of each other. Such a multi-user communication scenario is called interference channel (IC). Generally, it is desirable to achieve the best possible transmission rates for all the active pairs.
The channel between a pair of nodes can usually be estimated at the associated receiver. However, in most practical system setups, it is not possible to assume such channel knowledge in any other communication node especially the transmitting nodes. Thus, achieving the best possible transmission rates is difficult with knowledge of the channel state information at the receiver (CSIR) only and without any channel state information at the transmitters (CSIT).
Prior solutions have been inadequate for addressing this situation. Such inadequate solutions include using time division, frequency division, or code division multiple access schemes in order to orthogonalize the transmission from different users. However, joint transmissions from multiple sources usually achieve higher rates and overall throughput by using more sophisticated communication strategies. Such a scheme has also been considered for an interference channel. Generally, these approaches seek to mitigate the interference caused by other sources at each destination node and try to find the intended signal for this destination after some denoising or interference cancellation.
Dealing with interference is one of the main challenges of the multiuser communications in wireless environment. Practical wireless systems with multiple users are often called ‘interference limited’ due to the severe impact of the interference caused by the other users. Traditionally, anorthogonal transmission scheme in time, frequency, or code domain have been used to mitigate the interference. The broadcast nature of the wireless medium allows the intermediate communication nodes to hear the transmission and possibly generate a helper signal. Prior approaches in collaborative communication generally focus on the cooperation between the source node and the relay nodes in a single unicast problem. Nonetheless, the function of such relay nodes may be extended to mitigate the interference where multiple source-destination links communicate simultaneously.
The interference relay channel (IRC) has been examined where a single relay assists the communications between two interfering source-destination links. The role of the relay is then to generate signals not only to cooperate with the useful signal from the sources, but also to mitigate the interference at all destinations. One example of IRC is the shared relay channel (SRC) in which the interference from the other user is negligible and can be ignored. Thus, the role of the relay is only to generate the collaborative signal. The SRC has been analyzed from the perspective of broadcasting relay for orthogonal multiuser channels. The same channel model with multicast transmission has also been analyzed from the perspective of network coding by using the amplify-and-forward strategy. Capacity bounds for the fading and Gaussian multiple input multiple output (MIMO) SRC have been derived.
Although most of the prior work assumes static channels or perfect channel state information at the transmitters (CSIT), at least some efforts have addressed the scenario in which the channel for each link is only estimated at the corresponding receiver and is unknown to all other nodes. Since acquiring CSIT is especially hard in a network, the practical schemes that do not require CSIT (e.g., the practical rateless coding for the HD relay channel) are usually appealing. The rateless coding for single point-to-point channel has been studied for erasure channel, for the Gaussian channel, and as a general variable rate coding. The extension of the rateless codes in multiple access channels has also been considered. However, these solutions are inadequate
Accordingly, improved systems and methods for improving throughput in adaptive IR hybrid ARQ wireless transmission systems are required.